As a common nuclear power plant, a plant including a pressurized water reactor has been known, in which the pressurized water reactor is contained in a reactor containment vessel. In this case, with an assumption of an unusual event, a spray device that sprays cooling water in the reactor containment vessel is provided around the reactor containment vessel to reduce pressure in the reactor containment vessel.
In such nuclear power plants, it is known that a mesh basket in which a pH adjuster such as trisodium phosphate (TSP) is stored is located on a ground level (above the floor) near the external wall (for example, Nonpatent Literature 1).
With this configuration, at the time of an unusual event, cooling water is sprayed by the spray device, and the bottom of the reactor containment vessel is filled with the cooling water. The basket located above the floor in the reactor containment vessel is then inundated by the cooling water, and the pH adjuster stored in the basket is dissolved in the cooling water through the mesh. Thereafter, the cooling water in which the pH adjuster is dissolved (a pH adjuster solution) is circulated in the reactor containment vessel by the spray device, thus making it possible to adjust the pH level in the reactor containment vessel.
By adjusting the pH level in the reactor containment vessel, it is possible to hold radioactive iodine inside the reactor containment vessel in the pH adjuster solution or to suppress degradation of durability of structural material or various devices in the reactor containment vessel due to oxidization.